Noise suppressors are used in various hydraulic systems to compress or dampen the pulses of fluid which are flowing and pulsing through the hydraulic system. The pulses (or changes in fluid pressure) in the fluid flow cause wear on hydraulic systems. One type of noise suppressor comprises a housing having a pressure chamber defined between a flexible bladder and an interior surface of the housing. A pressurized gas is supplied to the pressure chamber. The interior of the bladder defines a fluid receiving chamber. The bladder is coaxially positioned over a tubular support or spool in the chamber. The support has radially extending perforations or holes. The fluid chamber receives the flow of fluid moving through the hydraulic system. The compressibility of the pulsed fluid is achieved as the fluid passes through the fluid chamber as follows: the peak of pulsing fluid passes out through the holes in the support and pushes against the bladder. The bladder expands into the pressure chamber. The pressurized gas on the opposite side of the bladder exerts a counter force on the bladder, thus minimizing or dampening the peak of the fluid pulse. The gas pressure pushes or acts against the bladder causing the bladder to be forced against the support spool. The pulsations of the fluid passing through the housing are absorbed or dampened in the fluid chamber due to the deflections (expansions and contractions) of the bladder and a consequent compression of the gas present in the pressure chamber.
The noise suppressor housings must also be adequately sealed to withstand the normal gas charge pressures, which are typically in the range of approximately 2000-3000 psi. The pulsations of the fluid cause the bladder to expand and contract and the bladder moves in the housing. In the past, it has been difficult to adequately seal the bladder in the housing of the noise suppressor so that fluid does not leak from the edges of the bladder into the gas pressure chamber and/or from the noise suppressor housing.
In addition, in currently used bladder-type noise suppressors, the normal gas charge pressures and the high temperatures of the fluids passing through the noise suppressors cause damage to the bladder. The bladder is under constant expansion and contraction pressures. Portions of the bladder come into repeated contact with the support stool. The bladder wears out at the areas on the bladder where the bladder contacts the spool. Portions of the bladder are removed from these contact areas due to the highly repetitive nature of the pulsing cycles the fluid flowing through the noise suppressor. In particular, the portions of the bladder adjacent the holes in the spool are prematurely worn or torn-away. That is, the edges of the holes in the spool wear away at the bladder causing the bladder to prematurely wear out and fail.
Previous attempts to prevent damage to the bladder have included the U.S. Pat. No. 4,759,387 which placed a helical wave band between a spool and a diaphragm. However, the diaphragm was still subject to undue wear. Other attempts include U.S. Pat. No. 4,628,964 which used a supporting cylinder comprised of a plurality of wire nets over a reinforcing cylinder. However, these previous attempts do not have sufficient durability needed in many types of hydraulic systems and the helical bands and wire nets tend to deform over time due to repeated exposure to pulsing fluids, thereby decreasing the effectiveness of the noise suppressors.
Therefore, there is a need for a noise suppressor which overcomes the above-described drawbacks and which has increased durability.